Synthesis and Na⁺ Ion Conductivity of Stoichiometric Na₃Zr₂Si₂PO₁₂ by Liquid-Phase Sintering with NaPO₃ Glass

• Main Authors: Yongzheng Ji, Tsuyoshi Honma, Takayuki Komatsu
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Materials
• Subjects: glass-ceramics; sodium ion-batteries; solid electrolyte; liquid-phase sintering
• Online Access: https://www.mdpi.com/1996-1944/14/14/3790

Sodium super ionic conductor (NASICON)-type Na₃Zr₂Si₂PO₁₂ (NZSP) with the advantages of the high ionic conductivity, stability and safety is one of the most famous solid-state electrolytes. NZSP, however, requires the high sintering temperature about 1200 °C and long sintering time in the conventional solid-state reaction (SSR) method. In this study, the liquid-phase sintering (LPS) method was applied to synthesize NZSP with the use of NaPO₃ glass with a low glass transition temperature of 292 °C. The formation of NZSP was confirmed by X-ray diffraction analyses in the samples obtained by the LPS method for the mixture of Na₂ZrSi₂O₇, ZrO₂, and NaPO₃ glass. The sample sintered at 1000 °C for 10 h exhibited a higher Na⁺ ion conductivity of 1.81 mS/cm at 100 °C and a lower activation energy of 0.18 eV compared with the samples prepared by the SSR method. It is proposed that a new LPE method is effective for the synthesis of NZSP and the NaPO₃ glass has a great contribution to the Na⁺ diffusion at the grain boundaries.